Three-dimensional printing, also known as additive manufacturing, is a process of making a three-dimensional solid object from a digital model of virtually any shape. Many three-dimensional printing technologies use an additive process in which successive layers of the part are built on top of previously deposited layers. Some of these technologies use inkjet printing, where one or more printheads eject successive layers of material. Three-dimensional printing is distinguishable from traditional object-forming techniques, which mostly rely on the removal of material from a work piece by a subtractive process, such as cutting or drilling.
During production of three-dimensional printed objects with an inkjet printer, the printer adjusts the relative position of one or more printheads within a comparatively narrow range distances from a surface of a substrate that receives the build material. In some instances the substrate is a support member in the three-dimensional object printer, while in other instances the substrate is an upper layer of an object that is formed in the three-dimensional object printer. The printer adjusts the relative distance between the printheads and the support member that holds the object to enable the printheads to print additional layers of material on an upper layer of the object as the printer forms the object from a series of layers of a build material. The printer controls the position of the printheads to ensure that the printheads are close enough to a surface of the substrate for precise and accurate placement of drops of the build material. The printer also controls the position of the printheads to maintain sufficient separation between the printhead and the substrate, which prevents the printed object from contacting the printhead which would result in clogging of the nozzles preventing the future firing or causing misfiring of the jets in addition to damage of the object being built.
During operation of a three-dimensional object printer, at least one of the support member or the printheads moves along the z-axis during the object printing process to accommodate the printed object that extends from the support member toward the printheads. Accurate measurements of the distance between the support member or upper layer of the object and the printheads enable the printheads to operate with improved precision and reliability. Consequently, improved systems and methods for identifying and controlling the separation between printheads and support members or objects in a three-dimensional object printer would be beneficial.